Oscillation generator



Feb. 14, 1939. 1 1 LAMB 2,146,961

OSC ILLATION GENERATOR Filed Jan, 10, 1933 J'aaaaes JLca, by m7, 752,Vfl/2% Patented Feb. 14, 1939 UNITED STATES PATENT OFFICE oscILLATIoNGENERATOR Application January 1o, 193s, serial No. esima 11 Claims.

My invention aims to provide improvements in electron tube oscillationgenerators.

In the drawing which illustrates preferred embodiments of my invention:-

Figure 1 is a wiring diagram of an embodiment of my invention in theformof a circuit using an indirectly heated cathode type of'electron tube;and

Fig. 2 is a wiring diagram showing my invention as adapted to a circuitincluding an electron tube of the directly heated cathode type.

My invention, as illustrated by the drawing.

is particularly useful as a stabilized electron tube oscillationgenerator and my improved circuits are particularly desirable becausethey are free from feed-back coupling between the outputl and`-control-grid circuit. Therefore, there is practically completeisolation of the output circuit from the control-grid circuit because ofelectrostatic screening of the inner anode which is maintained at groundradio-frequency potential. The output circuit is isolated from theoscillation generator circuit thereby preventing variations in theoutput circuit from affecting the frequency of oscillation whilepermitting ampliiied output from the frequency generating circuit to betransferred to the output circuit by electronic means.

'Ihe particular circuit illustrated in Figure 1 includes a four elementelectron tube I containing an indirectly heated electron-emittingcathode 2, cathode-heating means 3, a control element or grid 4, aninner anode 5 and an outer anode 6. A circuit containing Ian inductancecoil 1 and a variable capacitance I 'is connected between the cathode 2and inner anode 5. In this circuit is also connected `a fixedcapacitance 9. Another circuit is connected between the control elementI and the cathode 2 and in this circuit there is located a crystalsubstance I0 such as quartz and the like having piezo-electricproperties. This circuit also includes a suitable resistance I I inparallel with the crystal substance I0. The outer anode 6 is connectedto the rst described circuit at a point in that circuit common to theinductance "I, the variable capacitance ii and the xed capacitance 9. Inthis circuit is included an impedance or resistance I2 in series with aiixed capacitance I3, and the circuit is also connected to ground, asindicated, thereby also maintaining the inner anode at radio frequencyground potential. The output circuit is connected to the last "describedcircuit at opposite sides of the resistance I2 and includes a condenserI4 of suitable value.

-The cathode-heating means 3 may -be supplied (Cl. Z50-36) with energyfrom any suitable means I5 and the circuit connected between the supplyI5 and cathode-heating means 3 is maintained at substantially the samealternating current potential as the potential at the point ofconnection 5 between the circuit containing the condenser I3 and thecircuit containing the condenser 9. To accomplish this result I usefixed capacitances I6 having low reactance at the generated frequency.

'I'he plate supply means I1, together with the 10 resistance I8, isconnected into the circuits in the usual manner for supplying the properplate and grid potentials. The control grid I, by means of theresistance II. is maintained at an average potential which issubstantially negative as compared with the cathode 2.

Referring now to the particular embodiment of my invention illustratedin Fig. 2, I have shown a circuit which includes an electron tube I9having a directly heated cathode 20, instead of the indirectly heatedcathode 2 of the circuit shown in Fig. 1. Aside from the difference inthe tube cathode, the circuit is substantially the same as thatillustrated and described in connection with Fig. 1 with the necessarychanges in the cathodeheating circuit.

All of the elements shown in connection with the circuit illustrated byFig. 2 which are the same as those shown and described in connectionwith the circuit illustratedby Fig. 1 have been given the sameidentifying numerals as those used in describing the circuit shown inFig. 1.

My invention, whether embodied in the circuit shown in Fig. 1 or thatshown in Fig. 2, is particularly desirable, because it has manyadvantages over other circuits using the oscillating properties ofpiezo-electric substances of which I am aware. Heretofore there has beena feedback coupling from the output to the controlgrid circuit whichinterfered with stability of operation of the device as an oscillationgenerator. My improved circuit is particularly stable in operationbecause of the fact that the oscillation generating circuit, comprisingthe control-grid 4, inner anode 5 and cathode 2, is isolated fromvariations arising in the output circuit. In operation, my circuitdiiers from those of which I am aware because the adjustable tunedcircuit may be varied in value over a substantially wider range ofinductive reactance while persisting in oscillation at the frequencydetermined by the piezo-electric substance III. In this wide range oftuned circuit inductive reactance values the frequency of oscillation ismore independent of changes in circuit values and tube characteristics.55

Furthermore, my circuit, whether using the type of tube shown in Fig. lor that shown in Fig. 2, possesses inherent dynamic self-stabilizationproperties such that proportional changes in the inner and outeranode-supply voltages have substantially less effect on the frequency ofoscillation than is the case with other known circuits. Also, my circuithas substantially greater output atlfrequencies harmonically related'tothe frequencies of the stabilizing piezo-electric substance- I0. Theseadvantages are almost entirely due to the fact that the inner anode 5isl arranged to provide electro-static screening maintained at groundradio-frequency potential thereby preventing the output circuit fromaffecting the frequency of oscillation in the oscillation generatingcircuit. For instance, 'the harmonic generating ability results from theequivalence to two tubes performing the separate functions ofoscillation generation and distorting amplification. The oscillationgenerating circuit, including control grid 4, cathode 2 and inner anode5, performs as a triode of low amplification factor. The harmonicgenerating circuit includes those same elements and also the outer anode6, with cathode 2 and control grid 4 common to both, and with the inneranode 5 serving simply as a screen grid between those elements and theouter anode 6. This harmonic generating circuit is equivalent to afour-element tube of high amplification factor. Since the bias andexcitation to a high-mu screen grid tetrode are determined by theoperation of the triode generating circuit that is common to both, thebias and excitation are high for the tetrode, thereby satisfying theconditions for distorting operation and harmonic generation.

Some of the important advantages of my invention over other knowncircuits for oscillation generators may be summarized as follows:-

Oscillation persists over a substantially greater u range of tuning ofthe circuit including the inductance l and variable capacitance 8 whenadjusted to have inductive reactance for the resonance frequency of thepiezo-electric substance iii.

When the circuit including the inductance 'i and capacitance 8 isadjusted as just described variations in circuit capacitance, inductanceand resistance values and in electron tube characteristics havesubstantially less keect onthe frequency of oscillation.

Variations in anode voltages and cathode temperature have less eii'ecton frequency of oscillation.

Output of frequencies having harmonic relation to the frequency ofoscillation is very much increased.

Departure from normal output circuit conditions has no appreciableeiiect upon the frequency ci oscillation.

While i have illustrated and described preferred embodiments of myinvention, l do not wish to be limited thereby, because the scope of' myinvention is best defined by the following claims.

I claim:

1. An oscillation generator of the class described inclu an electron`tube having a outer anode and the iirst mentioned circuit and includingan impedance and a capacitance and an output circuit connected to thelast mentioned circuit and being isolated from the oscillationgenerating circuit because of the electrostatic screening of the inneranode thus preventing the variations in the output circuit fromaffecting the frequency of oscillation of the generator.

2. An oscillation generator of the class described including an electrontube having a cathode, a control element, an inner anode and an outeranode, a radio frequency ground connection to said inner anode, acircuit connected between the cathode and inner anode and includinginductance and variable capacitance, a crystal substance connectedbetween the control element and the cathode, a resistance in paralleltherewith, a circuit connected to the outer anode and the iirstmentioned circuit and including an impedance and a capacitance and anoutput circuit connected to the last mentioned circuit at opposite sidesof said impedance and being isolated from the oscillation generatingcircuit because ofthe electro-static screening of the inner anode thuspreventing the variations in the output circuit from affecting thefrequency of oscillation of the generator.

3. An oscillation generator having an electron tube provided with acathode, a control element, an inner anode and an outer anode, anoscillation generating circuit comprising said cathode, control elementand inner anode having a piezoelectric substance connected between thecontrol element and cathode and including' inductance and capacitance,an output circuit connected at one side thereof to said outer anode andat the other side thereof to said inner anode, whereby said inner anodeis common to both circuits, and means for maintaining said inner anodeat radio frequency ground potential for isolating said circuits fromeach other.

4. A constant frequency generator comprising an electron dischargedevice having an anode electrode, a grid electrode, and a. cathode, saidcathode comprising a heated surface electrode and a heating element, anelectromechanical vibrator connected between two of the electrodes ofsaid device, a high frequency output circuit connected between two oi'the electrodes of said device, and a high frequency impedance connectedbetween said heated surface electrode and ground, whereby the heatedsurface electrode iiuctuates in potential at a frequency correspondingto the frequency or vibration of said electromechanical vibrator.

5. An oscillation generator having an electron tube including a cathode,a control element, an inner anode, and an outer anode, a piezo-electricsubstance, the latter connected between said control element andcathode, means constituting an inductive reactance, circuit meansconnectz'ng one terminal of the latter to said cathode and connectingthe other terminal thereof to said inner anode and outer anode, andmeans for maintaining the last mentioned terminal oi' said inductivereactance at radio frequency ground potential.

6. An oscillation generator comprising an electron discharge devicehaving a cathode, and a plurality of cold electrodes, including a grid,screen grid and plate, a mechanical vibratile element connected betweensaid cathode and said grid, a tuned circuit connected between saidcathode and said screen grid and a load circuit connected between saidcathode and said anode, said screen grid circuit including a condenserand a ground connection thereto whereby to eectively ground said screengrid at the frequency oi' oscillation of said generator.

7. An oscillation generator of the class described including an electrontube having a cathode, a control element, an inner anode and an outeranode, means for maintaining said inner anode at substantially zeroradio frequency potential, a circuit connected between the cathode andinner anode and including inductance and capacitance, a piezo-electriccrystal connected between the control element and the cathode, aresistance in parallel therewith, a circuit connected to the outer anodeand the rst mentioned circuit and including an impedance and acapacitance and an output circuit coupled to the impedance of said lastmentioned circuit and being isolated from the oscillation generatingcircuit because of the electro-static screening of the inner anode thuspreventing the variations in the output circuit from aifecting thefrequency of oscillation of the generator.

8. An oscillation generator having an electron tube including a cathode,control element, inner anode and outer anode, an oscillation generatingcircuit comprising said cathode, control element, inner anode, apiezo-electric control element, an inductance and a capacitance, inwhich circuit said control element of said tube is connected throughsaid piezo-electric control element to said cathode and the latter isconnected through said inductance and capacitance to said inner anode,

an output circuit comprising said outer anode and a second capacitance,in which output circuit said outer anode is connected through saidsecond capacitance to a point on said rst mentioned circuit intermediatesaid inductance and capacitance and said inner anode, and a radiofrequency ground connection to' said point whereby said second mentionedcircuit' is shielded from said first mentioned circuit by said inneranode.

9. An oscillation generator having an electron tube including a cathode,control element, inner anode and outer anode, an 4oscillation generatingcircuit comprising said cathode, control element.

inner anode, a piezo-electric control element, an inductance and acapacitance, in which oscillation generating circuit said controlelement of said tube is connected through said piezo-electric controlelement to said cathode and the latter is connected through saidinductance and capacitance to said inner anode, an output circuitcomprising said outer anode, an impedance, and a `second capacitance, inwhich output circuit said outer anode is connected through saidimpedance and said second capacitance to said first mentioned circuit ata point in the latter between said inductance and capacitance and saidinner anode, a radio frequency ground connection to said point wherebysaid second named circuit is shielded from said rst named circuit bysaid inner anode, and an output circuit connected acrosssaid im-Dedance.

10. An oscillation generator having an electron tube including acathode, a control element, a rst anode, and a second anode, apiezo-electric 'substance, a tuned circuit including capacitive andinductive reactance, circuit means connecting said substance betweensaid control element and cathode, circuit means connecting one terminalof said tuned circuit to said cathode, said last two circuit meanshaving a portion in common, means connecting the other terminal of saidtuned circuit to said rst anode and to said second anode, and meansconnecting said other terminal of said tuned circuit to a point ofsubstantially ground radio frequency potential.

11. An oscillation generator having an electron tube including acathode, a control element, a first anode, and a Isecond anode, apiezo-electric crystal connected between said control element andcathode, a circuit comprising parallel react-

